how to encrypt string in php

Question

I want to make one function like It should have some secret key to mix with so that one one can break it

function encrypt($string)
{
$key ="mastermind"
return encryptfunc($string,$key)
}

and same thing for decryption

Answer 1

http://php.net/manual/en/book.mcrypt.php

Answer 2

If you are using PHP >= 5.3, the new openssl_encrypt might help you : it allows encryption of data using a wide range of cypher methods.

Those data can later be decrypted with openssl_decrypt, which, obviously, does the exact opposite.

And if you want to know which cypher functions you can use, openssl_get_cipher_methods will be helpful ;-)
There is quite a lot of those, it seems ^^

Here's a portion of code I posted on my blog some time ago, that should demonstrate the usage of those three functions :

$methods = openssl_get_cipher_methods();

var_dump($methods);

$texteACrypter = "he who doesn't do anything, doesn't go wrong -- Zeev Suraski";
$clefSecrete = "glop";

echo '<pre>';
foreach ($methods as $method) {
    $encrypted = openssl_encrypt($texteACrypter, $method, $clefSecrete);
    $decrypted = openssl_decrypt($encrypted, $method, $clefSecrete);
    echo $method . ' : ' . $encrypted . ' ; ' . $decrypted . "\n";
}
echo '</pre>';

The output I got when writting this was something like that :

bf-ecb : /nyRYCzQPE1sunxSBclxXBd7p7gl1fUnE80gBCS1NM4s3wS1Eho6rFHOOR73V9UtnolYW+flbiCwIKa/DYh5CQ== ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
bf-ofb : M9wwf140zhwHo98k8sj2MEXdogqXEQ+TjN81pebs2tmhNOsfU3jvMy91MBM76dWM7GVjeh95p8oDybDt ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
cast5-cbc : xKgdC1y654PFYW1rIjdevu8MsQOegvJoZx0KmMwb8aCHFmznxIQVy1yvAWR3bZztvGCGrM84WkpbG33pZcxUiQ== ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
cast5-cfb : t8ABR9mPvocRikrX0Kblq2rUXHiVnA/OnjR/mDJDq8+/nn6Z9yfPbpcpRat0lYqfVAcwlypT4A4KNq4S ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
cast5-ecb : xKgdC1y654NIzRl9gJqbhYKtmJoXBoFpgLhwgdtPtYB7VZ1tRHLX0MjErtfREMJBAonp48zngSiTKlsKV0/WhQ== ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
cast5-ofb : t8ABR9mPvofCv9+AKTcRO4Q0doYlavn8zRzLvV3dZk0niO7l20KloA4nUll4VN1B5n89T/IuGh9piPte ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
des-cbc : WrCiOVPU1ipF+0trwXyVZ/6cxiNVft+TK2+vAP0E57b9smf9x/cZlQQ4531aDX778S3YJeP/5/YulADXoHT/+Q== ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski
des-cfb : cDDlaifQN+hGOnGJ2xvGna7y8+qRxwQG+1DJBwQm/4abKgdZYUczC4+aOPGesZM1nKXjgoqB4+KTxGNo ; he who doesn't do anything, doesn't go wrong -- Zeev Suraski

And if you are not using PHP 5.3, you might want to take a look to the Mcrypt section of the manual, and functions such as mcrypt_encrypt ;-)

This is an interface to the mcrypt library, which supports a wide variety of block algorithms such as DES, TripleDES, Blowfish (default), 3-WAY, SAFER-SK64, SAFER-SK128, TWOFISH, TEA, RC2 and GOST in CBC, OFB, CFB and ECB cipher modes.

Answer 3

I'm not a crypto guy, but I use this kind of things :

function crypt($dataToEncrypt){
  $appKey = '%39d15#13P0£df458asdc%/dfr_A!8792*dskjfzaesdfpopdfo45s4dqd8d4fsd+dfd4s"Z1';
  $td = mcrypt_module_open(MCRYPT_SERPENT, '', MCRYPT_MODE_CBC, '');
  // Creates IV and gets key size
  $iv = mcrypt_create_iv(mcrypt_enc_get_iv_size($td), MCRYPT_DEV_RANDOM);
  $ks = mcrypt_enc_get_key_size($td);

  // Creates key from application key
  $key = substr($appKey, 0, $ks);

  // Initialization
  mcrypt_generic_init($td, $key, $iv);

  // Crypt data
  $encrypted = mcrypt_generic($td, $dataToEncrypt);

  // Close
  mcrypt_generic_deinit($td);
  mcrypt_module_close($td);
  return array($encrypted, $iv);
}

To decrypt a string you need the key and the initialization vector ($iv).

function decrypt($encryptedData, $iv){
  $appKey = '%39d15#13P0£df458asdc%/dfr_A!8792*dskjfzaesdfpopdfo45s4dqd8d4fsd+dfd4s"Z1';
  $td = mcrypt_module_open(MCRYPT_SERPENT, '', MCRYPT_MODE_CBC, '');
  // Gets key size
  $ks = mcrypt_enc_get_key_size($td);

  // Creates key from application key
  $key = substr($appKey, 0, $ks);

  // Initialization
  mcrypt_generic_init($td, $key, $iv);

  // Decrypt data
  $decrypted = mdecrypt_generic($td, $encryptedData);

  // Close
  mcrypt_generic_deinit($td);
  mcrypt_module_close($td);

  return trim($decrypted);
}